JPH0377469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a power switch shear failure test circuit, in particular, a power switch that has a power switch whose envelope peak value, which appears when the current flowing in a power transmission line having a shunt reactor is interrupted, is at commercial frequency. This invention relates to a power switch shear break test circuit that is optimal for use in applications that occur later than the cycle of the power switch.

The transmission voltage that was conventionally used for power transmission in Japan was
The voltage was less than 500KV, and shunt reactors were rarely connected directly to long-distance transmission lines. For example, in cases where the rated voltage is relatively low, such as in the 70KV class, a reactor was sometimes used to improve the power factor, but since both the rated voltage and rated capacity are small, various tests can be performed using the actual product. There were no particular problems.

However, it is said that UHV power transmission is scheduled to be put into practical use in the early 1980s, and various analyzes are currently being conducted. If a power transmission line with a shunt reactor breaks or a shunt reactor is connected to both ends of a non-stranded overhead power transmission line, one of the two circuits is in operation and the other circuit is suspended, and the One example of this is the analysis of the resistance of earthing switches that cut off electrostatically induced currents.

These are small currents and breaks in power transmission lines, or
In the case of a break in the earthing switch as described above, the computer calculation results show that the voltage waveform in which the maximum value of the envelope appears later than the period of the commercial frequency, as shown in Figure 1, is generated. , was found to be applied between the poles of a circuit breaker or switch. Since UHV-class equipment is very large and expensive, it is impractical to prepare an actual shunt reactor for each shear test due to the area of the test site and economic issues. It is possible. Therefore, it has been desired to develop a test circuit that can easily generate the voltage waveform shown in FIG. 1 by some method.

An object of the present invention is to develop a switch that can delay the maximum value of the envelope of a voltage waveform applied to a switch for electrostatic induced current of an unloaded power transmission line having a shunt reactor compared to the period of a commercial frequency. and provide disconnection test circuits.

In the present invention, power sources with slightly different frequencies are connected to both ends of the test switch, and one end thereof is grounded with an auxiliary disconnector.

FIG. 2 is a circuit diagram showing one embodiment of the present invention.

The primary winding of a transformer 5 is connected to the AC power supply 1 through a protective disconnector 2, a make switch 3, and an impedance 4, and a restart voltage adjustment resistor 6 and a capacitor 7 are connected to the secondary winding. A series circuit is connected. On the other hand, power supplies with similar configurations but slightly different frequencies are prepared. That is, AC power supply 1
1 is connected to the primary winding of a transformer 15 through a protective disconnector 12, a closing switch 13, and an impedance 14, and a series circuit of a restart voltage adjustment resistor 16 and a capacitor 17 is connected to the secondary winding. A test switch 8 is connected between the secondary winding output terminals of the transformers 5 and 15, and an auxiliary switch 9 is connected between the secondary output terminals of the transformer 15.

In the above configuration, the protective switch 2, 12,
With the test switch 8 and the auxiliary switch 9 closed, the closing switches 3 and 13 are closed while appropriately adjusting the voltages generated by the power supplies 1 and 11 and their mutual phase relationships. As a result, currents such as i shown in FIG. 1 flow through the test switch 8 and the auxiliary switch 9. Next, when the test switch 8 and the auxiliary switch 9 are opened almost simultaneously and the current i is interrupted, if the voltages of the power supplies 1 and 11 and the mutual phase relationship are appropriately selected, the test switch 8 A voltage waveform such as v shown in FIG. 1 appears between the poles. The reason for this will be explained by showing a formula.

If the voltage between both terminals of the test switch and ground is set as e ₁ and e ₂ and the phases are set as ₁ and ₂ as shown below, the following equation is given.

e ₁ = √2Esin (ω ₁ t+ ₁ ) ...(1) e ₂ = √2Esin (ω ₂ t+ ₂ ) ...(2) Therefore, the inter-electrode voltage v is expressed by the following formula.

v=e ₁ −e ₂ =√2E{sin(ω ₁ t+ ₁ )−sin(ω ₂ t+ ₂
)} =2√2E・cos[1/2{(ω ₁ +ω ₂ ) t+( ₁ + ₂ )}]・sin[1/2{(ω ₁ −ω ₂ )t+( ₁ − ₂ )}]
...(3) Therefore, for example, if the relationship is chosen as ₁ = ₂ = π/2, the interelectrode voltage v is expressed by the following formula.

v=2√2E・cos {(ω ₁ +ω ₂ )/2・t+π/2} ・sin{(ω ₁ −ω ₂ )/2・t} =−2√2E・sin{(ω ₁ +ω ₂ ) /2・t}sin {(ω ₁ +ω ₂ )/2・t} ...(4) In Figure 3, using equation (4), ω ₁ = 2π×50, ω ₂ =
It shows the calculated waveform of the voltage between electrodes v in the case of 2π×60. (ω ₁ + ω ₂ )/2=2π×55, |(ω ₁ −ω ₂
)
|/2=2π×5, so the frequency of the envelope is 5
Hz, so there is a maximum value of the envelope at 50 ms, which contains the 55 Hz oscillation.

Therefore, the circuit shown in Fig. 2, which can generate the voltage (e ₁ - e ₂ ) = v, can generate the required voltage waveform between poles, and can be used to eliminate gaps and breaks in power transmission lines with shunt reactors. It can also be used to test the earthing switches and disconnectors used for this purpose.

Note that there are power supplies on the left and right sides of the test switch 8 in FIG. 2, and in order to obtain the voltage between poles as shown in FIG.
It is necessary that the transient oscillating voltage waveforms appearing in the series circuit consisting of 17 are approximately equal. One method for this purpose is to select the resistors 6 and 16 to be relatively large so as to satisfy the non-vibration condition. Also,
As shown by dotted lines in FIG. 2, it is also advisable to further add a series circuit of a resistor and a capacitor for suppressing re-electromotive voltage to both ends of the test switch. As a result, high-frequency transient oscillations in the initial part of the electrode-to-electrode voltage are removed, and an ideal waveform as shown in Fig. 3 is obtained.
This has the effect that the breaking performance of the switch can be evaluated correctly.

In addition, in the circuit shown in Figure 2, even if the rated frequencies of both power supplies are the same, after the power to the drive motor of one generator is cut off, the rotation speed of the generator will decrease over time. By performing the shearing test at a selected time, the difference between the two power supply frequencies can be made continuously variable. Therefore, there is an advantage that the frequency of the envelope can be arbitrarily adjusted.

Also, as is clear from the above formula, ω ₁ and ω ₂
The polarity of the interelectrode voltage can also be changed by replacing the power supply.

As explained above, according to the present invention, it is possible to economically reduce the voltage between poles equivalent to that generated during an actual shear breakage test, without using an actual large and expensive shunt reactor with a high rated voltage. can occur.

[Brief explanation of drawings]

FIG. 1 is a diagram of voltage waveforms required for a test of a chopping block, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a diagram of a voltage waveform obtained by the present invention. 1, 11... AC power supply, 5, 15... Transformer, 6,
16... Resistor, 7, 17... Capacitor, 8... Test switch, 9... Auxiliary switch.

Claims (1)

[Claims] 1. In a shear test circuit used for testing a power switch, a first power supply section that applies an alternating current voltage to one electrode of the test switch at a predetermined time;
A second power supply unit that applies an AC voltage having a frequency different from that of the power supply unit to the other electrode of the test switch at a predetermined time, and a second power supply unit that is connected between each output terminal of the first and second power supply units. 1st and 2nd for adjusting the restart voltage
1. A shear breakage test circuit comprising: a re-electromotive voltage adjustment circuit; and an auxiliary switch connected between the output terminals of the second power supply section.